Tailor welded blanks (TWBs) are made by welding same or different materials having same/different properties into a single blank. They can be tailored to any specific shape and size. The formability of these blanks depend on material and geometric parameters like strength ratio and thickness ratio. This paper studies the effect of thickness ratio on the formability of tailor welded blanks by FE simulation. The formability is assessed by considering the Tensile and Limit Dome Height (LDH) tests. The weld region has been assumed as a line in all the simulations. While modeling tensile test, the ultimate tensile strength and the uniform elongation were monitored. In all LDH simulations, near plane strain condition is considered Uniaxial tensile testing shows that TWB formed will have lower elongation as compared to the base metal and the load bearing capacity will be comparable to that of thinner blank in case of transverse welded TWB. Thickness and thickness strain distribution along the blank show that the effective deforming area in a transversely welded TWB is that of the thinner blank. Both tests indicate that as the thickness ratio increases, the formability of TWB reduces.